Other noncurrent liabilities - Other Noncurrent Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Schedule Of Other Liabilities [Line Items]
Reserve for uncertain tax positions	$ 29.0	$ 26.9
Asset retirement obligations	10.1	3.9
Insurance claims and expenses	10.0	9.7
Employee benefits	9.9	10.3
Deferred income	1.0	1.1
Other	3.0	3.5
Total	$ 63.0	$ 55.4